Doctor blade device for applying, and scraping off, or for dosed application of flowable and spreadable substances

ABSTRACT

A doctor blade device has a magnetically-operated roller or a cylindrical rod enclosed in a sectional bar which does not influence the application process. The sectional bar surrounds this roller like a sleeve bearing and the sectional bar is pivotable around the axis of the application roller.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national phase of PCT/AT90/00066 filed Jul. 4,1990 and based upon Austrian national application A 1649/89 filed Jul.6, 1989 under the International Convention.

1. Field of the Invention

The invention relates, to a doctor blade device and as well as to aprocess using this doctor blade device.

2. Background of the Invention

A large number of processes of various kinds are known for applyingflowable substances to or scraping flowable substances from flatsurfaces, e.g. transfer surfaces. The processes include spreadingprocesses, coating processes using doctor rollers, applications withdosing rollers or applications by extrusion through nozzle slots.

SUMMARY OF THE INVENTION

The invention comprises a doctor blade device for applying, applying andscraping off, or for the metered application of flowable and spreadablesubstances, optionally with the use of a stencil, on preferably movingwebs of material or other flat surfaces with variable amounts to beapplied by means of a roller acting under magnetic pressure (directly orindirectly acting magnetic pressure) or by means of a cylindrical rod,whereby this application roller, or cylindrical rod cooperates with asectional bar co-influencing the application process.

According to the invention the sectional bar co-influencing theapplication process is mounted on the application roller or thecylindrical rod or is connected therewith and surrounds it like a sleevebearing basically over its entire length and in any case over the areaof the respective application width and covers a large portion of theshell surface of roller or of the cylindrical rod. The sectional bar isrotatable about the axis of the application roller or the cylindricalrod.

In short, the device of the invention consists in providing two mainworking components or namely an application roller, cylindrical rod anda sectional bar surrounding the cylindrical rod like a sleeve bearingand provided with a surface suited for application. The two componentsare connected to each other through an opening shaped like a sleevebearing so that operationally the assembly is almost a single-componentarticulated structure.

A large quantitative and qualitative variability results, as well asprecise, accurately reproducible, automated control capability of theapplication process, and at the same time an applicability to the mostvaried substrates and with various coating substances. It is alsopossible, depending on the substrate, substance and final product, toachieve an in-depth application, such as impregnation, or a lesspenetrating application of the substance or merely a sparse superficialcoating covering the entire surface of the substrate, so that thesubstrate can have an application surface with a novel appearance andwhich is modified from the point of view of weight and value increase,with improved utility. With the new process technique, the thickness ofthe applied layer can range for instance from 0.5 mm to 1.0 mm.

Each application process can be generally broken down approximately intothe following individual process steps:

(a) Supply of the substance with a surplus or with excessive pressureeither directly onto the substrate or to the application device,

(b) performing at least one step in order to meter the amount to beapplied (amount of coating per surface unit),

(c) performing at least one step in order to achieve the best possibleuniformity of application over the entire application width, and

(d) the actual transfer process.

A particularly advantageous characteristic of the new process techniqueaccording to the invention is that when devices produced for thisprocess are used, the previously described four discrete process steps(a) to (d) become so variable and mutually attuned, that with one andthe same technique of the invention, application device built accordingto the invention, a large variety of coating substances of verydifferent viscosities in very different amounts can be applied uniformlyto a great variety of substrates of any desired width.

It is particularly advantageous that, as mentioned before, within awidely variable application range, it is possible to set precisely therequired quantities and type of substance application required by therespective coating process and to keep it constant thereafter even whenthe process technique or the production kind requires changes in theapplication or web speed.

Besides, the application devices according to the invention areextraordinarily simple to handle. Furthermore, the application devicesaccording to the invention offer optimal premises for the mechanizationand automation of all aforedescribed technical process components whichquantitatively and qualitatively influence the coating process.

Due to this type of application, it is possible to produce on a verythin, on a very inexpensive or on a surface structure (substrate) havinga certain resistance, a certain physical property--e.g. a conglutinationcapability--a quasi novel product of a certain completely differentnature and having a different aspect, completely different from thesupporting substrate. It is also conceivable or possible to perform theprocess so that a layer-forming substance applied to asubstance-repellant support surface is fixed by a process step such aspolymerization, following immediately after the application, and thenfinally removed from the substance application surface required by thecoating process as an independent and subsequently usable final orintermediate product.

Another application possibility, which is very different from theabove-described use according to the invention is the application inconnection with flat or cylindrical stencils or cylindrical screens.This is the case when between the substrate surface coating deviceresting thereagainst thereagainst resting coating device producedaccording to the invention, a flat or a cylindrical stencil, or an openscreen or a cylindrical screen is inserted. This possible use of thedevice is further proof of the extremely versatile applicability and ofthe advantageous results of the characteristic features of theinvention.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features and advantages of the presentinvention will become more readily apparent from the followingdescription, reference being made to the accompanying drawing in which:

FIGS. 1 and 2 are diagrammatically sectional views which show anembodiment in two different positions; and

FIGS. 3 and 4 are diagrammatic sectional views which show furtherembodiments of the invention.

SPECIFIC DESCRIPTION

FIGS. 1 and 2 each show an application device 1 according to theinvention in its simplest construction, without mounting and swiveldevices, resting against a flat surface to be coated 2 and consisting ofthe sectional pivot bar 3 arranged on an application roller 4. The arrow5 shows the travel direction of the surface to be coated. It is alsoconceivable that the surface 2 to be coated is fixed and that theapplication device 1 is rolled upon the surface 2 to be coated in adirection opposite to the one indicated by arrow 5.

The travel direction indicated by arrow 6 is the same in bothafore-described travel variants of the device, and so is the swivelmotion and its effect in the process of the sectional bar around theaxis of the application roller 4 indicated by arrow 7.

This swivel motion of the sectional bar 3 causes a change in thepressure of the substance application in the substance contact area 8(equal substance contact time interval) in the area upstream of thetransfer, respectively removal process.

The surface 9 is rotated concentrically to the application roller 4,i.e. about this roller, respectively around the axis of the applicationroller 4.

Of utmost importance is the very large swivel range of the surface 9 incomparison to the heretofore known swivellable doctor blade devices. InFIG. 1, the swivel range through the two end positions of the sectionalbar 3 is indicated in a broken line and it can be 5° to 100°. Preferablyit amounts to approximately 90°. The reference numerals 29 and 28reproduce a corresponding point of the sectional bar in the twopositions. It has to be pointed out that, although it is advantageouswhen the sectional bar 3 surrounds the application roller 4 by twothirds, other proportions are also possible. However given the case,instead of the slide-on connection another type of connection has to beused, e.g. connection rods, a connection by weight load or axle endpivot, or also by magnetically caused attraction of the two components.

The rotated position of the sectional bar 3 shown in solid lines in FIG.1 exerts a very slight pressure (practically almost zero) on the bank ofthe coating substance 10 located in the area ahead of or upstream of theroller 4 underneath the substance application surface 9.

The rotated position of the sectional bar 3 shown in FIG. 2 causes theapplication surface 9 to exert a very high pressure on the applicationsubstance 10. Here it has to be additionally explained that the size ofthis substance-application pressure is also influenced by the viscosityand nature of the substance to be applied and by the speed of theapplication.

For the supply of the substance to the application device, which supplyis not shown in the drawing, there are various possibilities, whereby itis also conceivable to limit the substance contact area 8 in a directioncontrary to the direction of the arrow 5. In this way, a furtherincrease of the dynamic pressure of the substance can be achieved.

The arrangement of an application device according to the inventionrepresented in FIG. 2 illustrates the device, as well as the successiveprocess steps according to the invention. Due to the magnetic source notillustrated in this FIG. 2, the device 1, i.e. the application roller 4and the sectional bar 3 mounted onto it, i.e. both components workingtogether as a single-component device, are pressed uniformly against theapplication surface 2, over its entire length extending in axialdirection. Underneath the sectional accumulation surface 9 of the area 8and the bordering area 11 of the application roller 4 the actualapplication area controlling quantitatively and qualitatively theapplication effect is created and it consists of the two component areas8 and 11.

When the doctor blade device of the invention is used, the applicationprocess can be controlled through the following parameters. Length andshape (i.e. straight, curved, stepped) of the application surface 9,angular position, i.e. inclination of the application surface 9 withrespect to the application surface 2, height of the gap range,respectively the distance between the application surface 9 andapplication surface 2 in the application area 8 and in the applicationarea 11. Further, the gap range between application roller 4 andapplication surface 2, respectively table surface, conveyor belt or thelike supporting the web to be coated, which applies when the material tobe applied is compressable. The adjustment of the gap range takes placethrough:

(a) Adjustment of the magnetic pressure, by taking into considerationthe substance viscosity and the setting of the already mentionedparameters and

(b) by selecting the diameter of the application roller and of coursethe operating speed is also an important criterium.

A further important criterium is the relationship between the areaextension length 8 of the application surface 9 and the diameter of theapplication roller 4. It is possible to combine a relatively longsurface 9 with a relatively small roller diameter, or also a relativelyshort surface 9 with a relatively large roller diameter. The longer thesurface 9, the narrower the gap set between the 9 and 2 and the higherthe viscosity and the web speed, the stronger is the pressure exerted onthe substance by the surface 9 in the area 8 against the web 2 and withan equal force (i.e. counterforce) the application roller 4 is relievedof pressure.

Due to the cooperation according to the invention of the aforementionedparameters, a higher application pressure is generated in the gap area 8where there is no contact with the device than in any other case knownto the state of the art, because at an optimal setting of the amounts tobe applied, the edge zone of the application surface 9 (clearly shown inthe area 11 in FIG. 2) still does not touch the application surface 2when acting as a scraping blade and because--as just was explained--theapplication roller 4 is supported relieved of weight, but without beingcapable of changing its position, since the application roller is heldand encompassed by the sectional rod 3 and the sectional rod 3 restsagainst the auxiliary device 18 in the embodiment of FIG. 3.

As clearly shown in the figures, the individual component steps of theapplication process are the following: (a) the feeding of the substanceto be applied and the start of the substance/substrate contact takeplace in the area in front of the application device, a fact which isnot shown in the figures; as a result of the next process step (b), themetering (first of all the dosage of the amount) controlling thequantitative and qualitative parameters of the application process areperformed in the application zone formed by the path segments 8 and 11.Thereby it is of utmost technological importance that, while carryingout their application function, the two elements 3 and 4 of the deviceact as a device with a single-component construction and that due to therotation of the component 3 a control of the application parameters andtheir adjustment to the process become possible. Hereby, a fact of greatimportance to be considered is that this rotation creates the surfacepressure force of the substance application surface 9 against theapplication surface 2 or against the substance 10 between these twosurfaces, thus exerting a force upon the application roller 4 relievingits pressure against the surface 2, which in turn results in a furthereffect on the qualitative, respectively quantitative applicationparameters.

It is possible to bring the application device built and adjustedaccording to the invention to operate close to the limit of "floating onthe surface" of the application surface 2 or a substance layer 10gliding through underneath the support area of the application roller 4.In such a setting, it is possible to create novel application effectswhich have not been possible according to the state of the art, since inthe heretofore-known application processes and devices an increasingsubstance application pressure always corresponded to a proportionallyincreased doctor blade pressure. It also has to be mentioned bycomparison that in the application devices with rollers built accordingto the state of tee art and used in the heretofore-known processes, theabove-mentioned phenomenon of "floating on the surface" is extremelyundesirable, since it causes operational failure and applicationirregularities.

An additional feature of the invention relating to the above-describedapplication process and device techniques consists in the fact that theapplication element 4 can be selected at will to be either a rotatingroller or a nonrotatable cylindrical spreading rod. Furthermore, in theapplication device built according to the invention it is even possibleto make the process and device selection between an application withrotating roller or an application with a nonrotatble roller orcylindrical rod--even while the device is operating.

A further feature of the invention is the possibility to connect theapplication roller 4 with a drive not shown in the drawing, whereby thedrive can be set to be synchronized, to trail or to lead. This resultsin a further parameter for the quantitative and qualitative control ofthe application process.

The process step (c) takes place according to the path segment or thetime interval at the point or the moment when at the end of the pathsegment 11 the contact between the application element 4 and theapplication surface 2 is established.

The measure which is extremely important for the application processwithin the general course of this process is the uniform distribution ofsubstance over the entire application width or the length of theapplication device and it is carried out--as a second workingfunction--by the surface 9 of the sectional bar 3 due to the samecombination, i.e. the functional connection of the aforedescribed actingmanner of the surface 9 with the surface shell of the applicationelement 4 touched by the substance, whereby, as already described, thesubstance application pressure is generated.

The last component step of the process (d) takes place at the pathsegment where the path area 11 is ending and the application element 4is pressed by magnetic force over its entire length or its entireapplication width--against the substrate or application surface 2 or astencil located therebetween. The uniformity of this pressure over theentire length of the application device, respectively over the entireapplication width, resulting from the way specific to the invention inwhich this pressure is generated, is also an important factor infinalizing the even distribution over the entire width in the pathsegments 8 and 11.

An additional characteristic feature of the invention aiming at aprecise metering of the amounts to be applied per surface unit isachieved due a certain structure of the shell surface of the applicationroller 4 or the thereagainst pressed apex area of the cylindrical rod 4.The surface can for instance be smooth, rough or ribbed, or in the shellsurface of the application roller 4 a shallow-cup or grid-like structurecan be devised. In this case, the volume of such recesses in the surfaceof the application roller 4, or cylindrical rod play a part indetermining the resulting applied amounts.

In FIGS. 3 and 4, two variants of the mounting and adjustingarrangements of the application device are shown.

FIG. 3 shows a possible construction of the sectional swivel bar 3 withat least one part 12 through which the swivel motion 7 is induced by aregulating device in the application device, respectively transmitted tothe sectional swivel bar 3. The regulating parts 13, 14 causing theswivel motion 7 can be moved rectilinearly in the direction of the arrow15 so that the rectilinear motion 15 is converted into a swivel motion 7by the device 13, 14.

However, it is also conceivable that the swivel motion 7 can be executedby a regulating device making a swivel motion. The surface 16 of thesectional swivel bar 3 is rounded. However, this rounding could belimited only to a portion of the bar 3 or it could be located on aseparate component connected with bar 3.

The essential aspect in this additional characteristic feature of theinvention resides in the fact that this rounded portion is concentric tothe axis of the application roller, respectively the sectional bar 4 andthat this rounded surface 16 concentric with the swivel axis restsagainst a surface 17 of the buffer component 18, which can be displacedin the direction of the arrow 19, if necessary. It is possible to limitthe application device in direction of arrow 5 (travel direction) forinstance by means of a centrally located component 18. It is alsopossible to limit the advance possibilities of the application deviceand also to insure its parallel positioning by means of for instance twocomponents similar to 18, each located in the end areas of theapplication device.

In FIG. 4 a mounting and at the same time swivel actuating component 20is represented, which is mounted vertically movable at both ends of theapplication device 1. The application device is held and guided in aninclined recess 22 of the component 20, by means of a pivot 21 attachedto both ends of the sectional bar 3. In FIG. 4, the pivot 21 is locatedin the upper area of the recess 22.

When the component 20 is moved downwardly in the direction of arrow 23,the pivot 21 reaches first the median area of the recess 22,respectively in the position 24 shown in broken lines. When thecomponents 20 continue to move in the direction 23, finally the lowerarea of the recess 22, respectively the position 25 is reached. In FIG.4 there is also a magnetic source 26, which was not shown in FIGS. 1 to3 and which is connected with the working table 27.

Instead of being in the component 20, the recess 22 can be provided inthe sectional bar 3 or in another component rigidly connected with thisbar. Logically in this case the pin, bolt or the like would no longer beattached to the sectional bar 3, but to the component 20.

Instead of this embodiment of a magnetic source 26, 27 shown in FIG. 4,also other embodiments are conceivable, such as a magnetic roller. Butit is also conceivable to use instead of a magnetic roller or a magneticdevice 26, 27 a common roller of magnetizable steel, with the sectionalbar 3 or the roller 4 or both these elements being magnetically activeand exerting magnetic pressure on the steel roller.

The magnetic source establishes the position for the doctor blade deviceaccording to the invention, namely also in the operational state,besides it presses the doctor blade device to the extent required by theworking function of the application.

In the case of large application widths or length, it is also possibleto make the sectional bars 3 of a bending-slack material and to adjustthe doctor blade 4 thereto.

I claim:
 1. A coating apparatus comprising:a support for a material tobe coated; a doctor blade device juxtaposed with said support andprovided upstream thereof with a bank of substance to be coated ontosaid material, said doctor blade device comprising a cylindrical doctorelement pressed against said material and having an axis, and asectional bar partly surrounding said element and having a cylindricalsurface closely juxtaposed with said element over substantiallytwo-thirds of the circumference thereof, said bar receiving said elementlike a sleeve bearing over substantially the entire length of saidelement and being rotatable about said axis, said bar having anapplication surface swingable through an angle of substantially 5° to100° relative to said support and defining with said material a variableangle through which said substance is pressed as said device and saidmaterial are moved relatively to coat said substance onto said materialwith said device; means operatively connected with said bar for varyingthe angle included between said application surface and said material;and means for pressing said device against said material and saidsupport.
 2. The apparatus defined in claim 1 wherein said element is anonrotatable cylindrical rod.
 3. The apparatus defined in claim 1wherein said element is a rotatable cylindrical roller.
 4. The apparatusdefined in claim 1 wherein at least one of said element and said barcontain a magnetically attractable metal and said means for pressingsaid device against said material is at least one magnetic field source.5. The apparatus defined in claim 1 wherein said application surface isa planar surface.
 6. The apparatus defined in claim 1 wherein said meansfor varying the angle included between said application surface and saidmaterial includes a device capable of rectilinear displacement and meansfor converting said rectilinear displacement into angular displacementof said bar about said axis.
 7. The apparatus defined in claim 1 whereinsaid bar forms one of a plurality of bars of various shapes, widths andapplication surface configurations, said bars being interchangeablymounted on said element.
 8. The apparatus defined in claim 1 whereinsaid bar has a rounded surface at a downstream side of said device andsaid apparatus further comprises a member braced against said roundedsurface of said bar.